1. Field of the Invention
The present invention relates generally to treatment of breathing disorders. In particular, the present invention relates to systems and methods for controlling breathing of a patient by maintaining specific levels of carbon dioxide (“CO2”) dissolved in the patient's arterial blood.
2. Background of the Invention
Sleep-disordered breathing (“SDB”) includes all syndromes that pose breathing difficulties during sleep. These include obstructive sleep apnea (“OSA”), mixed sleep apnea (“MSA”), central sleep apnea (“CSA”), Cheyne-Stokes respiration (“CSR”), and others. Some form of SDB occurs in approximately 3-5% of the U.S. population.
While anatomical problems such as obesity or an abnormally narrow upper airway may be a cause of some SDB, neurological difficulties in controlling levels of blood gases, such as CO2 and oxygen (“O2”), are increasingly being recognized as important contributors to the disease. This is especially true of the “central” syndromes, MSA, CSA and CSR, which may account for as much as 20% of all SDB. Changes in the neurological system that controls the blood gases often produce unsteady respiratory patterns that cause arousals from sleep. These changes are accompanied by severe spikes in blood pressure and release of stress hormones that can cause long-term damage to a number of organ systems. Additionally, some SDB syndromes involve abnormal overall levels of blood gases. For example, low levels of dissolved CO2 in arterial blood are frequently encountered, which represents a clinical problem. Thus, there is a need to stabilize respiration and establish appropriate blood gas levels by restoring normal control of blood gases when treating SDB.